Ultrasmall TiO_<i>x</i> Nanoparticles Rich in Oxygen Vacancies Synthesized through a Simple Strategy for Ultrahigh‐Rate Lithium‐Ion Batteries

Abstract

Abstract Ultrasmall particle size (&lt;10 nm) and rich oxygen vacancies are two sought‐after characteristics for titanium dioxide (TiO 2 ) to achieve high performance, namely, high rate and high storage capacity, when being used as an anode in lithium‐ion batteries (LIBs). However, free TiO 2 particles simultaneously possessing both characteristics have not been reported, owing to the synthetic challenges. In this study, we report novel TiO 2 nanoparticles with ultrasmall size (ca. 5–8 nm) as well as rich oxygen vacancies synthesized through a simple strategy. Specifically, porous carbon nanoparticles were used to confine the TiO 2 precursor in the nanosized pores in the carbon nanoparticles, which were annealed at a high temperature in argon to produce the TiO 2 nanoparticles with ultrasmall size and rich oxygen vacancies and subsequently annealed in air to burn away the carbon nanoparticles to afford the so‐called TiO x nanoparticles in a quantitative yield. The obtained anatase TiO x nanoparticles showed an exceptional ultrahigh‐rate lithium storage capability. A record reversible specific capacity of 235 mAh g −1 was achieved at the current density of 0.1 A g −1 . Even at an ultrahigh rate of 10 A g −1 (ca. 59 C), it still delivered a specific capacity of 90 mAh g −1 , which is five times that of the electrode made with the commercial anatase TiO 2 nanoparticles. Furthermore, this electrode also showed an excellent cycling performance with capacity retentions of 87 % and 90 % at high rates of 1 A g −1 and 5 A g −1 , respectively, after 1000 cycles. The strategy reported in this work can potentially be a universal method for synthesis of other metal oxides with ultrasmall particle size and rich oxygen vacancies.

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